JPH0555038B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat roll fixing device used in electrophotographic devices and the like, and particularly to a structure for temperature control thereof.

[Conventional technology]

A heat roll fixing device is a device for melting and fixing unfixed toner on a recording paper, and a conventional one mainly consists of two rolls, a heat roll and a back-up roll.

The heat roll has an infrared lamp inside, and this infrared lamp is electrically controlled to maintain the heat roll surface temperature at around 180° C. during the fixing operation.

Heat rolls are usually made of a cylinder with a wall thickness of around 3 mm made of a metal with high thermal conductivity, such as aluminum, and the surface layer is coated with a toner release material such as polytetrafluoroethylene (Teflon). ing.

On the other hand, for back-up rolls, rubber rolls such as silicone rubber are used.

A heat roll fixing device with such a configuration is
A recording paper is passed between a heat roll and a back-up roll, and at this time, the unfixed toner on the recording paper is heated by the heat roll and fixed on the recording paper.

[Problem that the invention seeks to solve]

However, in such a conventional heat roll fixing device, since the heat roll and infrared lamp have a large heat capacity, the start-up time usually takes about 1 to 5 minutes, and there is a delay between fixing operations, that is, when the fixing operation is stopped. In this case, it is necessary to maintain the temperature of the heat roll at or near the fixing temperature.

Therefore, there is a problem in that it takes a long time to start up after the power is turned on, and it is inconvenient, and power loss occurs to maintain the heat roll temperature during stopping, that is, waiting.

Moreover, when maintaining the heat roll at a high temperature, it is necessary to continue exhausting the air outside the apparatus using a fan, etc., in order to prevent the temperature of the photosensitive drum from rising. Since the distance needs to be 10 cm or more, there is a problem of increasing the size of electrophotographic equipment and the like.

Another conventional example is a "fixing temperature control device" described in Japanese Patent Application Laid-open No. 192065/1983.

This conventional example has a structure in which the surface of an insulating fixing roll, ie, a heat roll, made of ceramic or the like is coated with a planar heating element.

The sheet heating element and heat roll shown here are
Although the heat capacity is not specified, the heat roll is made of an electrical insulator with relatively high thermal conductivity, such as ceramic, so during fixing, the entire heat roll is kept heated to the same level as the fixing temperature.

In addition, as yet another conventional example, Utility Model Publication No. 58-48680
There is a "fixing roll" described in the publication.

This conventional example includes a fixing roll having a structure in which a heat-resistant insulating film and a heat-generating resistor are provided on the inner surface of a conductive core;
In other words, although a heat roll is shown, it is necessary to heat and maintain the entire surface of the fixing roll to the fixing temperature in order to bring its surface to the fixing temperature.

Therefore, in these two conventional examples, it is necessary to heat and maintain the entire fixing roll, so the rise time of the fixing roll cannot be shortened.
In other words, there is a problem in that the rise time cannot be reduced to within a few seconds.

The present invention has been made to solve these problems, and aims to provide a heat roll fixing device that can shorten the start-up time of the device, does not require high temperature maintenance while stopped, and consumes less power. This is the purpose.

[Means for solving problems]

In order to achieve this object, the present invention involves passing a recording paper between a rotating heat roll and a back-up roll, heating the unfixed toner on the recording paper by the heat roll, and fixing the toner on the recording paper. In the roll fixing device, the heat roll includes a support roll, a heat insulating layer provided on the outer circumferential surface of the support roll, and a heat insulating layer extending in the axial direction of the support roll and backed up with the heat roll on the outer circumference of the heat insulating layer. A plurality of ribbon-shaped heater films formed with a width equal to or narrower than the width of the contact portion with the roll, and a ribbon-shaped heater film formed at both ends connected to each heater film and having an end at at least one of them are as described above. a heater electrode having a width approximately equal to the width of the heater film;
The structure includes a coating layer that covers each of the heater films, and a tongue that is arranged at a contact portion between the heat roll and the back-up roll and that contacts the heater electrode with a width equivalent to the width of the contact portion. A piece-shaped sliding electrode, a detection means for detecting the temperature of a heater membrane electrically connected to the sliding electrode via a heater electrode, and power is supplied to the heater membrane through the sliding electrode and the heater electrode. The heater film is characterized by comprising a power control section that generates heat by heating the heater film and controls power supply to the heater film according to the temperature detected by the detection means.

[Effect]

In the present invention having such a configuration, when the heat roll is rotated, the heater electrode sent to the contact area between the heat roll and the backup roll comes into contact with the sliding electrode and is connected to the heater electrode. Electric power is supplied from the power control section to the heater membrane, which generates heat, a detection means detects the temperature of the heated heater membrane, and the power control section supplies power to the heater membrane according to the detected temperature. When the heater electrode passes the contact portion, the heater electrode separates from the sliding electrode and the power supply to the heater film is cut off, so that the heater film stops generating heat and the next The heater electrode contacts the sliding electrode, and power is supplied from the power control unit to the heater membrane connected to the heater electrode to generate heat, and power control to this heater membrane is performed in the same manner as described above.

In this way, the heater film sequentially generates heat at the contact portion between the heat roll and the back-up roll, so when the recording paper is passed between the heat roll and the back-up roll, the unfixed toner on the recording paper is transferred to the heater film. are sequentially heated and fixed on the recording paper.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a schematic sectional view showing an embodiment of a heat roll fixing device according to the present invention.

In the figure, 1 is a heat roll, and this heat roll 1 includes a heat insulating layer 3 formed on the outer circumferential surface of a support roll 2, and a plurality of heat insulating layers 3 extending in the axial direction of the support roll 2 and formed on the outer circumference. The heater film 4 is composed of a ribbon-shaped heater film 4 and a toner release coating layer 5 coated on the outermost periphery of the heater film 4.

The thermal insulation layer 3 is made of asbestos, polyimide resin, silicone resin, etc., which has electrical insulation and heat resistance, and has a thermal conductivity of 10 ^-2 J/cm・s・k or less, and has a thickness of 1 mm. A heat insulating structure is obtained by forming the above structure.

The heater film 4 is made of a material such as NiCr or Ni-W-P, and is formed by vapor deposition, sputtering, thick film printing, dipping, or plating to extend in the axial direction of the support roll 2 and in the circumferential direction of the thermal insulation layer 3. are formed at intervals.

The width of the heater film 4 is equal to or narrower than the width of the contact area between the heat roll 1 and the backup roll 6 (hereinafter abbreviated as "nip width") necessary for toner fixation.

The coating layer 5 is made of polytetrafluoroethylene (Tetron registered trademark) or the like, which has good toner releasability so that the toner does not stick.

Further, in order to shorten the rise time of the heat roll 1, the heat capacity of the heater film 4 and the coating layer 5 is reduced to provide a heat insulating structure.

That is, in this embodiment, the thickness of the heater film 4 is set to 20 μm or less, and the thickness of the coating layer 5 is set to 20 μm or less.
By making the thickness 10 μm or less, their heat capacity is reduced.

The back up roller 6 disposed opposite to the heat roll 1 is a rubber roll made of silicone rubber or the like.

7 is a recording paper loaded with unfixed toner.

FIG. 2 is a partial perspective view showing an embodiment of the heat roll fixing device according to the present invention.

In the figure, reference numeral 8 denotes a heater electrode, and the heater electrode 8 is provided at both ends of each heater film 4 in one-to-one correspondence.

Reference numeral 9 denotes a fixed sliding electrode, which is mechanically pressed against one or more heater electrodes 8 on the side where the heat roll 1 and the backup roller 6 are in contact with each other, and is pressed against the nip width. The sliding electrode 9 is in contact with the heater electrode 8 with a width comparable to that of the sliding electrode 9, and the sliding electrode 9 is designed to be electrically connected to the heat electrode 8 even when the heat roll 1 rotates.

10 is a power control unit that supplies power to the heater membrane 4 through the sliding electrode 9 and heater electrode 8 to generate Joule heat; 11 is disposed between the sliding electrode 9 and the power control unit 10. This resistor 11 serves as a temperature detection means, and has both ends 11a and 11b.
is connected so that the potential of .

That is, the resistance of the heater film 4 increases as the temperature rises, and the current value decreases when driven at a constant potential.
The temperature of the heater film 4 can be detected by the potential difference between a and 11b, and the power control section 10 controls the power supplied to the heater film 4 based on the temperature detected by the resistor 11.

Note that one side of the heater electrode 8 may be used as a common electrode, and in the case of DC power, this common electrode side may be grounded.

Further, the resistance value of the heater film 4 in this embodiment is determined with respect to the supply voltage so that Joule heat can be generated that is 1.5 to 2 times the amount of heat required for fixing the toner.

Next, the operation of the above configuration will be explained.

First, the heat roll 1 is rotated in the direction of arrow A in FIG. 1 by a drive motor (not shown), and at the same time, the backup roll 6 is rotated in the direction of arrow B in FIG.

During the fixing operation, the recording paper 7 carrying unfixed toner is inserted into the contact area between the heat roll 1 and the backup roll 6 and passes through.

On the other hand, as the heat roll 1 rotates, the heater electrode 8 sequentially comes into contact with the sliding electrode 9 at the nip portion, so that power is sequentially supplied from the power control section 10 to the heater membrane 4 and generates heat.

The temperature of the heater film 4 that generates heat is detected as a potential difference between both ends 11a and 11b of the resistor 11, and the power control unit 10 controls the power supply to the heater film 4 according to this detected temperature, and sets the heater film 4. Raise to temperature.

The rise time for one heater film 4 in this embodiment is about 0.1 seconds when fixing a sheet width equivalent to A4 paper with a power of 400 W.

Since the heater film 4 is raised to the set temperature in this manner, the unfixed toner on the recording paper 7 is thermally melted by the heater film 4 and fixed on the recording paper 7.

When this heater film 4 passes through the contact part with the back-up roll 6, the sliding electrode 9 and the heater electrode 8
Since the connection is cut off, power is no longer supplied and no heat is generated, but the heater electrode 8 of the next heater membrane 4 comes into contact with the sliding electrode 9 and power is supplied, so the heater membranes are connected one after another. 4 has a fever.

Control of power supply to these heater films 4 is also performed in the same manner as described above.

Therefore, the unfixed toner on the recording paper 7 is fixed on the recording paper 7 one after another, and as the recording paper 7 passes between the heat roll 1 and the back-up roll 6, all the unfixed toner is fixed. .

In addition, as a configuration other than this example, the support roll 2
If the heater film 4 is made of a material with high thermal conductivity such as metal, and the thermal insulating layer is formed as thin as 1 mm or less, it will not be possible to create an insulating structure for the heater film 4, and the rise time will be long, resulting in heat loss due to thermal conduction. Therefore, the supporting roll may be made of a material with low thermal conductivity and may be integrated with the heat insulating layer.

〔Effect of the invention〕

As explained above, in the present invention, power is supplied only to the heater film sent to the contact area between the heat roll and the back-up roll to generate heat, and the other heater films are prevented from generating heat. The thermal isolation structure around the roll fixing device can be relaxed, which brings about the effect that the heat roll fixing device and the photosensitive drum can be brought closer to each other and the entire device can be downsized.

In addition, by forming a heater film on the outer peripheral surface of the heat insulating layer to create a heat insulating structure, heat loss due to heat conduction is suppressed, which reduces startup time and improves fixing after power is turned on. Even if the heat roll temperature is lowered to the room temperature level while the operation is stopped, there is no problem in starting the next operation, so it is also possible to eliminate power consumption during the stop, that is, waiting.

Furthermore, the width of each heater film is formed to be equal to or narrower than the width of the contact portion between the heat roll and the back-up roll, and the temperature of the heater film generated at this contact portion is detected by a temperature detection means, Since the power control section controls the power supply to the heater membrane based on the detected temperature, fine power control is possible, and power consumption can be minimized.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention;
FIG. 2 is a partial perspective view showing one embodiment of the present invention. 1...Heat roll, 2...Support roll, 3...
...Thermal insulation layer, 4... Heater film, 5... Covering layer, 6
...Backlash Prowl, 7...Recording paper, 8...
Heater electrode, 9...Sliding electrode, 10...Power control unit, 11...Resistor, 11a, 11b...Both ends.

Claims (1)

[Scope of Claims] 1. A heat roll fixing device in which a recording paper is passed between a rotating heat roll and a back-up roll, and unfixed toner on the recording paper is heated by the heat roll and fixed to the recording paper. , the heat roll includes a support roll, a heat insulation layer provided on the outer peripheral surface of the support roll, and a contact between the heat roll and the back-up roll that extends in the axial direction of the support roll and is formed on the outer peripheral surface of the heat insulation layer. A plurality of ribbon-shaped heater films formed with a width equal to or narrower than the width of the heater film, and a ribbon-shaped heater film formed at both ends connected to each heater film and having an end on at least one of the heater films have a width equal to or smaller than the width of the heater film. A heater electrode having a width approximately equal to the width of the heater electrode, and a coating layer covering each of the heater films, the heater electrode having a width approximately equal to the width of the contact portion, and a coating layer that covers each of the heater films. a tongue-shaped sliding electrode that contacts the heater electrode with a width of , a detection means for detecting the temperature of a heater membrane electrically connected to the sliding electrode via the heater electrode, and the sliding electrode and the heater. A heat roll comprising: a power control unit that supplies power to the heater film through an electrode to generate heat, and controls the power supply to the heater film in accordance with the temperature detected by the detection means. Fuser.